1. Field of the Invention
The present invention relates to a battery protection device. More particularly, the present invention relates to a battery protection device that prevents fire and/or explosion caused by abnormal heat generation, and to a battery having the battery protection device.
2. Description of the Related Art
As a driving power source for portable electronic devices, secondary batteries that can be repeatedly charged and discharged and have a relatively low environmental load have been developed. In a secondary battery, a separator may be installed between a positive electrode and a negative electrode. The charging/discharging of the secondary battery may be realized as lithium ions (Li+) travel between the positive and negative electrodes. Thus, secondary batteries can be repeatedly used.
However, if a secondary battery is overcharged, or if a number of charge/discharge cycles of the secondary battery exceeds an advised range, lithium dendrites may form. When lithium dendrites are formed, they may penetrate the separator and make contact with the positive electrode, thereby causing a short circuit.
A short circuit may cause excess heat to be generated in the battery. Thus, an electrolyte provided in the separator may boil. Such boiling may cause the battery to catch on fire or explode.
In order to prevent this, a protection device may be provided in the secondary battery. Such a protection device may detect abnormal heat generation or a pressure increase, e.g., using a thermal relay, and may reduce a transport current of a battery circuit, safely discharging a residual battery capacity (electric energy), thus enhancing safety of the battery.
However, since the thermal relay is unrecoverable once abnormal heat generation occurs in the second battery, the secondary battery cannot be reused. Other solutions, such as an unrecoverable fuse, a recoverable poly-switch or bimetal switch, a current/voltage detection protective circuit, and a combination thereof have been proposed. However, with the use of these other solutions, the manufacturing process is complicated and the number of parts increases, thereby increasing manufacturing costs.